The present invention relates to a solenoid for an electromagnetic valve which is mounted to an electromagnetic valve to drive a valve member for switching flow paths.
As shown in FIG. 4, an electromagnetic valve 50 which has been previously proposed by the present applicant comprises a valve portion 51 provided inside with an unillustrated valve member for switching flow paths and a solenoid portion 52 which is connected to the valve portion 51 to drive the valve member, and the valve member of the valve portion 51 is constituted so as to be opened/closed according to pushing effected by a push rod 60.
The solenoid portion 52 is constituted by assembling, in a cylindrical magnetic body case 53 provided at one end with an opening portion connected with the valve portion 51, a bobbin 55 having a coil 54 wound around an outer periphery thereof, a magnetic body plate 59 which has been attached to an end side of the opening of the magnetic body case 53, and a fixed iron core 56 and a movable iron core 58 which have been inserted into central holes of the magnetic body plate 59 and the bobbin 55.
A proximal end portion of the movable iron core 58 is opposed to the fixed iron core 56, and a distal end portion thereof is fitted with a cap 61 serving as both a stopper and a spring seat. This cap 61 has a butting portion 61c at its proximal end portion, and the butting portion serves such that, when the movable iron core 58 has been attracted to the fixed iron core 56, the butting portion 61c abuts on the magnetic body plate 59 to stop the movable iron core 58 just before the movable iron core 58 strikes against the fixed iron core 56, and it has a function for preventing impact noise from being generated due to an impact.
Also, a flange portion 61a is provided at an outer periphery of the cap 61, and a return spring 57 is provided between the flange portion 61a and the magnetic body plate 59, so that the movable iron core 58 is always biased by the force of the return spring 57 in a direction of pressing the push rod 60 towards the valve portion 51 side. Furthermore, a recessed portion 61b provided on an inner peripheral face of the cap 61 is engaged with a projection portion 58a provided on the movable iron core 58, so that the cap 61 is prevented from falling off from the movable iron core 58.
In the electromagnetic valve 50 having such a constitution, when the coil 54 in the solenoid portion 52 is energized, as shown on a right half in FIG. 4, the movable iron core 58 is attracted to a magnetic pole surface 56c of the fixed iron core 56 and the butting portion 61a of the cap 61 abuts on the magnetic body plate 59 to stop. On the other hand, in a de-energized state of the coil, as shown on a left half in FIG. 4, the movable iron core 58 is separated from the magnetic pole surface 56c by biasing force of a return spring 57 to push the push rod 59 so that the valve member is driven in linkage with the push rod.
Now, in general, in such a solenoid for an electromagnetic valve, there often occurs a case that such a member as the cap 61 is attached on a distal end of the movable iron core 58 for the use object as a stopper, a spring seat or the like. Such a member is easy to receive a force acting to come off from the movable iron core by action of an external force such as an impact force or a biasing force of a spring occurring at a time of operation of the movable iron core, for example, in such a case that the member functions as a stopper or spring seat. For this reason, such a member must securely be mounted to the movable iron core so as not to displace or fall off easily. In addition, a constitution for attaching the member must be simplified as much as possible and a mounting work must be simplified.
In the above known example, since the recessed portion 61b of the cap 61 is engaged with the projection portion 58a of the movable iron core 58, the cap 61 does not fall off from the movable iron core 58. However, since the cap 61 must be fitted on the movable iron core 58 from a distal end side of the iron core while a force exceeding a resistance force due to the projection portion 58a is being applied, a large force is required so that a mounting work becomes troublesome.
In view of the above, an problem of the present invention is to allow a member having a function as a stopper, a spring seat or the like to be securely mounted to a distal end of a movable iron core in a solenoid for an electromagnetic valve with a simple constitution.
In order to solve the above problem, a solenoid of the present invention comprises: a bobbin made from non-magnetic body, which has a iron core hole extending in an axial direction and which has a coil wound on an outer periphery thereof; a magnetic body case which covers a side face of the bobbin and one end face thereof in the axial direction; an annular magnetic body plate coupled to the magnetic body case on the side of the other end face of the bobbin; a movable iron core which is received movably in the iron core hole of the bobbin; a fixed magnetic pole member which attracts the movable iron core; and a return spring which biases the movable iron core in a direction of separating from the fixed magnetic pole member.
Then, the movable iron core has a main body portion with an even section fitted into the iron core hole, and a flange portion with an even section formed on a portion extending from the iron core hole of the distal end of the main body portion, a ring is fixedly fitted on an outer periphery of the distal end of the movable iron core at a position where it spans over the main body portion and the flange portion. Also, the ring has a first portion which is positioned on a distal end side and which has a large diameter hole in which the flange portion is fitted and a second portion which is positioned on a proximal end side and which has a small diameter hole in which the main body portion is fitted.
Since the present invention has such a constitution, the ring can easily be mounted on the movable iron core with a relatively small force by fitting the ring from the proximal end portion of the main body portion of the small diameter of the movable iron core to move it towards the distal end side. Also, even when such an external force as an impact force or a biasing force of the spring at an operation time of the movable iron core acts on the ring in a direction in which the ring is caused to move to the distal end side of the movable iron core, since an engaging force of the ring with the flange portion is rather strengthened by the external force, a mounting state of the ring is further secured.
According to a specific constitution aspect of the present invention, the ring is made from synthetic resin and is formed with a stopper for the movable iron core, and the proximal end portion of the second portion in the ring is provided with a butting portion which abuts on the magnetic body plate when the movable iron core is attracted to the fixed magnetic pole member. Also, this ring may be a spring seat for the return spring. In this case, a flange-shaped spring receiving portion which supports one end of the return spring is provided on the outer periphery of the ring.
In the present invention, the sectional shapes of the iron core hole, the movable iron core and the ring may respectively be formed in an elliptic shape. In this case, it is preferable that a recessed groove for forming a gap between the movable iron core and the iron core hole is provided in an axial direction on the main body portion of the movable iron core on either one or both of the sides faces in the short diameter direction of the ellipse.
Also, the movable iron core may be formed of a metal sintered body obtained by compression-molding metal powder to sinter the same.